[mythtv-users] Transcoding and aspect ratio (DVB-T)

Chris Pinkham cpinkham at bc2va.org
Fri Mar 31 23:42:10 UTC 2006

* On Fri Mar 31, 2006 at 10:15:38AM +0100, Ian Grant wrote:
> Does anyone know any different, or have any ideas, etc.?'
> Eventually, I got a reply:
> 'the problem with the nuv format is that there is no way to properly 
> specify the aspect ratio.
> remember that the aspect can change in a recording (commercial break, 
> start/end of show and so on)
> there is one field in the nuv file header for aspect ratio, but this is 
> always set to 4:3 by mythtv.

Not sure who said that, but I know it's not what I told you in the thread
you linked to.  I said that I personally had fixed mythtranscode and
NuppelVideoRecorder a long time ago to support specifying the proper
aspect ratio in the nuv header.  It works great for my transcoded
recordings.  My 4:3 recordings show as 4:3 when displayed in
NuppelVideoPlayer and mplayer (with the patch applied) and my 16:9
recordings show as 16:9 in NVP and mplayer.

Do you know if you can change aspect ratios in a mpeg4 stream?  If so,
and libavcodec supports it, then it should be easy to add, but I'm not sure
if it is possible (but, I'm not a video expert either).

> So, it seems the ideal solution would be to have mythtranscode write the 
> aspect ratio into the MPEG4 stream, as per the original MPEG2 file (I 
> assume it's written per-frame, or something).
> Does anyone know if this is possible, or if the Myth developers are even 
> aware of this?

You were talking to one of them (ie, me) in the thread you linked to above.
This isn't an issue for me, so I haven't got the itch to research it, but
if you can find out, I can modify the mpeg4 transcoder to support it.


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